Process analyzers and instruments are commonly used for the monitoring, optimization and control of processes which include hazardous or flammable gases and liquids. Typical applications include gas processing, refining, chemical and petro-chemical processes. It is a requirement in many of these applications for the instrumentation and analyzers to meet strict safety criteria in order to protect against fire and explosion. Examples of process instrumentation and analyzers that must meet such safety criteria include gas or liquid analyzers, such as a combustion analyzer or process gas chromatograph, and/or other process indicators.
There are a number of known designs and methods for providing hazardous area protection depending on the industry and world area. Variations are often driven by safety standards in each area or jurisdiction. Methods of protection include explosion proof/flameproof electronics enclosures; purging electronics enclosures with non-flammable gas; employing electronics that comply with one or more intrinsic safety specifications, and others.
A typical flameproof or explosion proof enclosure includes a heavy metal casting that is usually constructed from aluminum. A challenge for such products is to provide an easy to use operator interface that still complies with the appropriate safety criteria. Such operator interface options typically include non-contact keypad buttons such as infrared, magnetic or Hall-effect keypad buttons, or complex operator rod keypads.
Known operator interfaces are thus complex, expensive, and typically are difficult to use. Moreover, such interfaces also lack the feel of a more conventional membrane keypad used on general purpose industrial and household equipment.
Providing a low-cost flameproof operator interface that has a tactile feel similar to known conventional membrane keypads would advance the art of operator interfaces in hazardous or explosive areas.